On the combination of CFD and rate-based modelling in the simulation of reactive separation processes

Reactive separations (RS) combining mass transfer with simultaneous chemical reactions inside one column unit provide an important synergistic effect and bring about several advantages. However, the design and modelling of the RS columns are more sophisticated than traditional operations and thus rigorous and reliable description methods are necessary. Besides, in RS, the influence of column internals increases significantly. These internals have to enhance both separation and reaction and maintain a sound balance between them. This is the reason why, frequently, the application of process-specific column internals, rather than internals currently available on the market, is desirable. In this paper, a new modelling methodology for RS is suggested which exploits a combination of modem CFD facilities and the rate-based process simulation approach. The task of CFD is to obtain hydrodynamic and mass transfer correlations necessary for the process description. These correlations are then used in a rate-based simulator to determine required column profiles of the process variables. Both CFD and process simulation are described and illustrated with industrially relevant examples. The sensitivity studies provide information on the influence of important hardware parameters and show optimisation tendencies. The CFD simulations can be regarded as virtual experiments carried out without really existing column units which help to predict the performance of the internals by varying their geometrical and structural properties. Supplemented by the rate-based simulations, the suggested method can be viewed as a principal way towards the virtual prototyping of internals. (c) 2004 Elsevier B.V. All rights reserved.